VARIATION IN ZOOPLANKTON BIOMASS DURING A PERIOD (1982-2000) OF WIDELY VARYING HYDROLOGIC REGIMES AND PRIMARY PRODUCTIVITY IN HYPERSALINE MONO LAKE, CALIFORNIA

Varying hydrologic regimes associated with unusual climatic events and human activities over the past two decades have resulted in a wide range of annual primary productivities (150 - 1000 g C m-2 yr-1) in Mono Lake. However, despite this more than 6-fold variation in primary production, average daily zooplankton biomass has only varied about 3-fold (5.3 – 17.6 g m-2) during the period. Two factors account for this muted variation in zooplankton biomass. First, much of the observed variation in primary production occurs during the winter-spring period when Artemia, the sole macrozooplankton in Mono Lake, is largely absent. Second, the variation in algal biomass and productivity during the period when Artemia are present leads to variation in reproductive output. Cyst production has varied nearly three-fold during the period (2.5 - 6.7 million m-2).